This invention relates to a method and an apparatus for determining the location of points on a three dimensional thing, contour, size or the like of the same by measuring coordinates of points on the thing.
Various types of three dimensional coordinate measuring apparatuses have been used to measure the coordinates of points on a three dimensional thing to determine the contour, size or the like. Such apparatus naturally have limits in space on the measurement which the apparatuses can achieve with the apparatus fixed at one position. Accordingly, when a three dimensional thing is large so that the area of the thing to be measured exceeds the limits of measurement as stated above, it is required to divide the area into a plurality of sections and to measure the respective sections by changing the position of the thing relative to the apparatus. Thus, in such measurement, the coordinates of the points on the respective sections are not defined by a single reference coordinate system which is determined with respect to the thing and, thus, it is impossible to determine the contour, size or the like of the entire thing directly from such measured coordinates.
Accordingly, in the past, in order to make it easy to transform such measured coordinates into coordinates in a reference coordinate system on the thing, an operator usually took the following operation: a coordinate axis or axes of the coordinate measuring apparatus was made to be aligned with or parallel to the coordinate axes which are predetermined with respect to the thing by adjusting the relative position between the apparatus and the thing or by using a conventional coordinate transformation apparatus and, when the thing is moved to effect measurements of respective sections on the thing, the thing is moved keeping a predetermined portion of the thing parallel to or parpendicular to the reference coordinate axis or the reference coordinate surface of the coordinate measuring apparatus. However, keeping such relation between the thing and the apparatus is difficult and, thus, it is difficult to effect accurate measurement. Further, if the thing has no straight line or a flat plane thereon, such operation per se is impossible.